PYE 697 Chassis: No Field output and tuning unstable

Symptom

When this set was obtained there was no field output and the tuning was unstable. Replacing the field output transistors and the 33V tuning line stabilising diode D5 cured these faults. Tow faults remain.

First, just after teh picture comes up, a confetti-like line, wavering and shimmering, appears from top to bottom and about two-thirds of the way across the screen. At its most intense it causes hum on sound. The shimmering line and hum disappear within a few minuets, and do not reappear until the set is next switched on. Disconnecting the degaussing coils has no effect on this symptom.

The second fault is a tendency for every second line in strong red or yellow areas to have no or wrong colour -this condition appears to me intermittent.

Solution

The symptoms during warm up could well be caused by corona, due to dust around the e.h.t. parts, or to a poor aquadag or chassis connection. The other trouble os Hanoverian blinds and usually means the the delay line pahes adjustmet L32A in front of the chrominance delay line is misadjusted.